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BIO EXAM 1
Terms in this set (166)
What characterizes living things?
-A barrier separation external and internal spaces
-Metabolic processes to provide energy and materials
-Growth and reproduction
-Capacity to adapt to changing conditions
What is the scientific method?
What is the difference between a hypothesis and a theory?
Hypothesis is a tentative explanation or prediction whereas a theory is well-supported by scientific studies and generally regarded as "fact"
How are hypotheses tested? Can a hypothesis or theory be "proved?"
Tested by experiments . Hypothesis and theory CANNOT be proved, only supported or not supported
Pasteur's experiments on spontaneous generation
Pasteur believed that cells are only produced by other cells. Bacteria grew in straight-necked flask but was gathered in the swan necked flask and couldn't reach the existing cells. His hypothesis was supported that cells come from cells.
Narrowly focused prediction from wider theory; often mathematical in nature
Can there be selection on populations (phenotypic selection) without evolution occurring?
Genetic basis, then it could be passed on.
Ex: Purple hair could be selected for but it cannot be genetically passed on.
What is the relationship between genotype and phenotype?
Genotypic: Genetic traits
Phenotype: physical traits
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
A change in the genetic composition of a population over time
Ability of an organism to survive and reproduce in its environment
A characteristic that improves an individual's ability to survive and reproduce in a particular environment.
What were the major ideas concerning the origins of and changes in species prior to the theory of natural selection?
-Species are highly diverse
-The more similar species are, the more closely they tend to be located to one another
-Many species have gone extinct
-Modern species tend to differ from extinct species
All living things were created by God and fit in Scala Naturae
Organisms are complex and well-adapted because they were made by God
Catastrophism vs Uniformitarianism (or Gradualism)
Catastrophism is explanation of Earth's current state whereas Uniformitarianism is forces acting on the earth now are the same as they were in the past.
Lamarck and his hypotheses about evolution of species
Spontaneous generation produces simple species that evolve over time due to two forces:
-"Drive towards complexity": Lineages evolve as a result of innate force trending to move species up in Scala Naturae
-"Adaptive force": Individuals change in response to their needs and then passed to offspring
What was the subject of Malthus' famous essay, and why was it important to Darwin and Wallace?
Increases in food production cannot keep pace with growth of inhabitants. It was important to Darwin and Wallace because they believed all species tend to produce more offspring that parents.
Who developed the theory of evolution by natural selection, and when was this occurring? What famous book first presented this idea?
Charles Darwin, 1838, "On the Origin of Species by Natural Selection"
What observations and logical conclusions support the idea of natural selection?
Conclusion 1: Not all individuals survive and there is a "struggle for existence" between individuals and population
Conclusion 2: Some individuals will happen t be better suited for their environment than others, and so will be more likely to be among those that survive and reproduce
Conclusion 3: Selection results in changes in the average traits of a population over time such that adaptation increases.
What is the meaning of "fitness" and "adaptation" in an evolutionary context?
Fitness: Ability of an individual to successfully reproduce
Adaptation: A trait that improves the fitness of an animal
What types of evidence support the occurrence of evolution by natural selection?
Evolution results in genetic differences between populations due to selection for different traits
1. Individuals in a population differ in their traits
2. The differences affect survival and/or reproduction
3. The differences are heritable
What is the difference between a comparative and an experimental study?
Comparative approach compares populations or species from naturally-differing environments whereas experimental actively manipulates the population to create difference
What is a common-garden experiment?
Bring population samples into lab and raise in the same conditions
Evidence for longer-term evolutionary events
Antibiotic resistance in bacteria
Have features that are intermediate between those of hypothesized ancestors and later descendant species
Global distribution of species
The taxonometric way of classifying organisms is based on similarities between different organisms. A biologist named Carolus Linnaeus started this naming system. He also chose to use Latin words. Taxonomy used to be called Systematics. That system grouped animals and plants by characteristics and relationships.
Homologous and vestigial traits
Vestigial structures are often homologous to structures that are functioning normally in other species. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time.
Understand - and avoid - the common misconceptions about natural selection and evolution
Natural Selection is not all-powerful; it does not produce perfection
Organisms do not always get BETTER from evolution
What is the difference between adaptation and acclimatization/acclimation?
Acclimation, on the other hand, is temporary adaptation to gradual changes in the natural habitat. It only occurs in the lifespan of the organism and doesn't affect evolution patterns of its species.
Ex: when a fresh water fish is caught and placed in an aquarium. The location may change but since sea water is not used, the new habitat pretty much mimics the old one, although it may experience a slight change in temperature and the space to swim around. Eventually the fish learns to adapt by acclimation to its new surroundings.
Why do evolutionary biologists avoid the terms "higher" and "lower" in reference to species?
They are not meaningful labels for species . Instead, "more" or "less" derived
What are examples of cases where evolution is NOT progressive?
Species may become more complex or less complex, or gain or lose traits
Why shouldn't individuals act "for the good of the species"?
Evolution will happen when the species continues to adapt naturally.
What are the constraints that can prevent or slow adaptation?
Lack of genetic variation, if a population is genetically identical, there is no mutation to change a species.
What are vestigial traits and what do they tell us about selection?
Vestigial structures are inherited from ancestors, but have lost much or all of their original function due to different selection pressures acting on the descendant.
EXAMPLE: The hipbones of bottlenose dolphins are vestigial structures. In their ancestors, hipbones played a role in terrestrial locomotion. However, as the dolphin lineage adapted to life at sea, this function was lost.
Theory of Forms
Scala Naturae ----> Ladder of Nature/ Great Chain of being that ranks all living things
God creates variation on general body plans with each new creation
Wrote Principles of Geology which Darwin read on his travels as a naturalist
Believed spontaneous generation produces simple species that evolve over time
Observed the problems that came with human population growth. There wouldn't be enough food for everybody
A principle that states that geologic change occurs suddenly
The component of the natural selection process in which some traits result in greater fitness than others
A random error in gene replication that leads to a change
Single-locus & multi-locus traits
Single-locus: A phenotypic trait controlled by a single gene
Multi-locus: Trait influenced by many genes
Transitional form/ species
A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.
A specific role of a species within an ecosystem, including its use of resources, and relationships with other species.
Traits that were useful in ancestors that are inherited today, but that have lost their original use.
Natural selection can work only with available variation. If appropriate mutations do not arise, selection cannot operate.
Adaptations are constrained because all traits evolve from previously existing traits
The act of giving up one benefit in order to gain another, greater benefit
What is meant by Mendelian inheritance?
Predicts offspring for particular parents
-Applies to diploid sexual species
-Each gene, or locus, has two copies in each individual
-Each locus can have slightly different forms, or alleles
Calculations involved in determining Hardy-Weinberg equilibrium
1. Pool alleles in entire population to get allele frequencies
2. Use allele frequencies to calculate expected frequencies of each genotype
What conditions must be true for a population to be in H-W equilibrium? What does it mean if populations show deviations from H-W?
To be in H-W equilibrium, there must be no changes in allele frequency. If populations deviate from H-W, evolution is occuring
What are the reasons non-random mating may occur?
1. Mate chosen based on similarity or dissimilarity to self (Assortative)
2. Mate chosen based on close familial relationship (Inbreeding)
3. Particular traits are more generally attractive to mates (Sexual Selection)
What are the two types of assortative mating? Be familiar with examples
1. Positive assortative mating for height
2. Negative assortative mating for MHC complex
Why is inbreeding generally detrimental to fitness?
Increasing number of homozygous recessive deleterious alleles
What are the different types of sexual selection, and what are some potential results of sexual selection? Be familiar with examples.
1. Sexual Dimorphism:
Results- Males can potentially father more offspring, but women are limited because they carry the offspring for months. Males are often showier or larger. (Peacocks)
2. Sexual Selection via Female Choice:
Results- Sexually attractive males are those that contribute more to offspring fitness (Buck with a big rack)
3. Sexual Selection via Male-male competition:
Results- Winners gain access to more females so females may have limited choice of males (Rhino beetles fighting)
Why does sexual dimorphism usually involve larger and/or showier males rather than females?
Due to differences in energy input into gametes and/or offspring care. The fundamental asymmetry of sex is that females usually invest more in offspring that males do. So females are choosy and males often have to compete for mates.
How might sexual selection differ from non-sexual natural selection in its effects on species?
Desirable individuals leave more offspring on average
What is meant by "founder effect" and "bottleneck"?
Founder effect: Small group founds a new population
Bottleneck: Populations that temporarily drop in size
How do population size and time affect genetic drift?
Effects are larger in smaller populations
What is meant by the term "fixation" with regard to alleles?
Chance losses of a few allele copies can have larger effects in small population, including complete loss of an allele
How can alleles move between populations?
Individuals moving between populations
How are allele frequencies affected by gene flow?
Migrating individuals tend to have allele frequency of the source population
What general types of mutations can occur?
1. Single-locus mutations
2. Gene duplication
3. Gene deletion
Are most mutations beneficial or deleterious?
Be familiar with an example of mutation introducing variation for selection to act on
Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population.
Ex: Populations of wild cheetahs have very low genetic variation. Because wild cheetahs are threatened, their species has a very low genetic diversity. This low genetic diversity means they are often susceptible to disease and often pass on lethal recessive mutations; only about 5% of cheetahs survive to adulthood.
Differences among stabilizing, directional and disruptive selection, and how the examples illustrate these processes
1. Stabilizing: Favors intermediate values. Normally reduces genetic variability.
Ex: Babies in between the highest and lowest birth weights were deemed healthier than those extremely light or extremely heavy.
2. Directional: Favors one end of distribution. Tends to reduce genetic variability by elimination unfavored phenotype.
Ex: Red squirrels reply on stored seeds in the winter so individuals with a lower metabolic rate have higher survival rates.
3. Disruptive: Favors both ends of distribution. Tends to maintain genetic variability.
Ex: Birds with small beaks were good for small nuts, birds with big beaks were good for big nuts. Birds with average beaks were too small for big nuts and too big for small nuts.
Balancing selection can help maintain genetic diversity, and be familiar with the example of sickle-cell anemia as an example of heterozygote advantage
Sickle cell trait, which protects against malaria in heterozygotes, but causes a deadly disease in homozygotes.
Different forms of a gene
Location of a gene on a chromosome
Diploid is containing two complete sets of chromosomes from parents, while haploid only has one set of chromosomes from parents.
Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus
Combined genetic information of all the members of a particular population
A change in the allele frequency of a population as a result of chance events rather than natural selection
Fixation (of an allele)
The change in a gene pool from a situation where there exists at least two variants of a particular gene (allele) to a situation where only one of the alleles remains
Movement of alleles into or out of a population due to the migration of individuals to or from the population
Source/ sink populations
Gene flow typically means the movement of alleles from one population (the source) to another (the sink)
• Usually involves individuals moving between populations
• May involve just gametes (e.g., pollen)
• Sink tends to become more like source
• Changes in frequency of sink's existing alleles
• (Re) introduction of alleles not in sink
• Greater rates of migration leads to greater similarity between populations
The generation of extra copies of a gene in a genome over evolutionary time. A mechanism by which genomes can acquire new functions.
A mutation in which a part of a chromosome or a sequence of DNA is lost during DNA replication
Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.
Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population
when individuals with similar genotypes - typically relatives - breed with each other and produce offspring that have an impaired ability to survive and reproduce
Sexual Selection/ Sexual dimorphism
Sexual selection occurs when individuals differ in their ability to obtain mates based on phenotype whereas Sexual Dimorphism is the differences in phenotype of sexes.
Fundamental asymmetry of sex
Females usually invest more in their offspring than males do
Female choice (intersexual selection)
Females may chose mates on the basis of physical characteristics that signal male genetic quality and resources of parental care provided by male.
Male-male competition (intrasexual selection)
Favors traits in males that help them compete:
-Large overall size
- Larger or more effective structures for competing
What are three major ways in which a species can be defined? What are the advantages and disadvantages of each?
1. Morphological species:
- Easy to measure
- Many species have already been categorized using this method
- Can be applied to fossil species
- Different taxonomies may emphasize different traits
- Convergent evolution may cause confusion
-How much morphological difference makes a different species?
2. Biological Species:
-Reflects the potential for the group to share alleles and thus evolve as a unit
-Difficult to assess potential for breeding among different populations or fossils
- Doesn't apply to asexual species
3. Phylogenetic Species:
-Allows quantifiable measurement of differences among groups
-Time-consuming to assess, so robust datasets currently limited
-How much phylogenetic distance makes a different species?
What is allopatric speciation?
A physical barrier divides one population into two or more populations
What's the difference between colonization and vicariance?
-fragmented habitats (ponds and lakes)
-Change in water course
-Major geological events
Why do species tend to speciate once separated?
The physical separation forces an independent evolution apart from each other
What is sympatric speciation?
A species evolves into a new species without a physical barrier
What are different ways sympatric speciation can occur?
1. Disruptive selection
How does disruptive selection allow sympatric speciation to occur?
Low fitness of intermediate phenotypes leads to two sub-groups within a population
Why is polyploidy important to sympatric speciation?
Reproductive isolation is typical, due to incompatible gametes
When populations or species that have started to diverge genetically come back into contact, what are the possible outcomes?
1. Little evolution has occurred, so gene flow allows gene pools to remix
2. Sufficient evolution for prezygotic isolation to occur. Species remain distinct
3. Something in between
-Formation of new species
How does reinforcement work?
Matings between individuals from divergent groups may produce less fit offspring, or none at all -- postzygotic isolation
How can a hybrid zone remain persistent over time?
If hybrids have a higher fitness level than parents in some locations, then hybrids could become a third species
How can re-contact lead to the production of new species?
Binomial nomenclature is the formal naming system for living things that all scientists use. It gives every species a two-part scientific name. For example, a ladybug found in the United States goes by the fancy name of Harmonia axyridis. The first part of a scientific name, like Harmonia, is called the genus.
Carolus Linnaeus is the father of taxonomy, which is the system of classifying and naming organisms. One of his contributions was the development of a hierarchical system of classification of nature.
Prezygotic isolation/ Postzygotic isolation
Prezygotic isolation prevents the fertilization of eggs while postzygotic isolation prevents the formation of fertile offspring.
Autopolyploidy vs Allopolyploidy
The first occurs within species and the second occurs between species
May represent an intermediate environment, favoring an intermediate phenotype.
How are phylogenies reconstructed? What kinds of data are used and what for?
What are the terms for different parts of a phylogenetic tree and the traits that are mapped onto trees?
What is the difference between a homoplasy and a homology?
Both terms refer to sets of biological characteristics that are shared by two or more species (hence the prefix homo), but homology indicates that the shared characteristic came from a common ancestor species, while homoplasy refers to a shared characteristic that evolved independently in each species.
What are the advantages and disadvantages of morphological versus genetic reconstruction of phylogenies?
What can branch lengths in a phylogeny represent?
How is the timing (in years) of branching events in the tree estimated?
How does radiometric dating work?
Overtime, some isotopes decay at a constant rate. Changes in isotope/elemental ratios reflect elapsed time.
How are fossils useful in reconstructing tress? Why are so few fossils formed? What are the different types of fossils?
1. Useful because they offer a look at what ancestral forms looked like
2. The process of fossilization is difficult and the biological material is fragile
3. Compression, cast, pre-mineralized, and intact
What is the molecular clock, and what is the principal behind it?
The changes in hemoglobin sequence over time, based on extant hemoglobin samples and fossil record. It can help estimate the rate of mutation over time.
How do fossils form?
Most fossils form when living things die and are buried by sediments. The sediments slowly harden into rock and preserve the shapes of the organisms.
What kind of information can and can't we get from fossils?
- Reconstruct parts of the complete tree of life not seen in extant organisms
-See what ancestral forms looked like
-Test genetically-generated trees against evidence
-Tell time in which it died
-The exact species
What are some limitations of the fossil record?
Fossil record only gives us information about the possible basic builds of the ceased creature(s).
Synapomorphy / plesiomorphy
Synapomorphy: A characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.
Plesiomorphy: Refers to the ancestral trait state, usually in reference to a derived trait state
The independent evolution of similar features in species of different lineages
Radiometric dating / stratigraphic dating
Radiometric: Uses half-lives of radioactive elements
Stratigraphic: Done once timeline is established
Molecular clock / silent mutation / neutral mutation
Molecular clock: The average rate at which a species' genome accumulates mutations, used to measure their evolutionary divergence and in other calculations.
Silent Mutation: Base substitutions that result in no change of the amino acid or amino acid functionality when the altered messenger RNA (mRNA) is translated
Neutral Mutation: Changes in DNA sequence that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce
Know the approximate start and end time of the Precambrian, Paleozoic, Mesozoic and Cenozoic
Precambrian: 4,600- 540 mya
Paleozoic: 540- 250 mya
Mesozoic: 250- 65 mya
Cenozoic: 65- 0 mya
Origin of Life
Origin of eukaryotic life
2 billion years ago
Origin of complex multicellular life
Invasion of land by plants, arthropods and vertebrates
First seed plants
First flowering plants
What is the Cambrian Explosion? What factor or factors probably resulted in this event?
Rapid diversification of animal groups from simple forms
What is " adaptive radiation", and what are two factors that can trigger this process? Be familiar with examples from the textbook.
Adaptive radiation: Rapid and extensive diversification of an evolutionary group
1. Open ecological niches
2. Key adaptation
What is a "key adaptation"?
A new feature that greatly improves the evolutionary potential of a group
What are the different reasons an ecological niches might be open?
1. Early in the evolutionary history of a region
2. Following an extinction event
What is a mass extinction event?
When the rate of extinction is higher than the natural background extinction rate.
What happened during the Cretaceous-Tertiary extinction, and how do we know?
Massive asteroid impact and we know because we lost 75% of terrestrial and marine species in complex patterns
When did the biggest known extinction event occur?
Permian- Triassic Extinction
The dinosaur extinction that occurred when a large meteor hit the earth. 65 mya.
Second pair of jaws in the throat in some fish
Burgess Shale fossils
Incredible array of fossils, brand new animals with eyes. every modern phyla is present in these fossils
How do prokaryotes differ from eukaryotes?
Prokaryotes are smaller and lack a true membrane delimited nucleus their DNA is in the cytoplasm (e.g. bacteria). Viruses are packets of DNA or RNA without cytoplasm; they are not technically alive.
Eukaryotes are larger, have a membrane enclosed nucleus containing their DNA (e.g. cells of our body) and are more complex.
What is the phylogenetic relationship among the three domains? What evidence do we have for this?
Defining characteristics of green algae
Defining characteristics of Bryophytes (mosses)
Defining characteristics of Pteridophyta (ferns)
Defining characteristics of Gymnosperms
Defining characteristics of Angiosperms
What group is pinus (pine)?
What group is Ginkgo?
What group is Arabidopsis (Cress) ?
What group is flowering plants?
What group is mosses?
What group is Ulva?
What group is cycads?
What group is fern?
Flowers, seeds roots
Vascular tissue, cuticle, cell walls
Stomata, sporophyte-dominant life cycle, gametophyte-dominant life cycle
Order major plant groups appeared
Major innovations that arose in each clade
What traits were necessary for the transition to land?
What new advantage does each more derived plant group have over previous groups?
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